Fuel injection control arrangement for internal combustion engines



July 28, 1970 P SCHMIDT FUEL INJECTION CONTROL ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed Oct. 18. 1 968 4 shee cssheet 1 MW m J .W z 1/24. $1 wrllllwlllllllwwwlu HMB 9 .l 2 2 INVENTOR Peter SCHM|DT his ATTORNEY July 2 8, 1970 P. SCHMIDT 3,521,606

FUEL lNJ ECTION CONTROL ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed Oct. 18, 1968 4 Shoots-Sheet 8 F163 U2 f "P a I c I J I I .1

II] I7 INVENTOR PeterSCHMlDT his ATTORNEY July 28, 1970 P. SCHMIDT 3,521,606

FUEL INJECTION CONTROL ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed Oct. 18, 1968 4 Sheets-Sheet 5 ti FIG.8

INVENTOR Peter SCHMIDT W/n/f 5461 his ATTORNEY July 28, 1970 P. SCHMIDT 3,521,606

FUELINJECTION CONTROL ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Filed Oct. 18, 1968 4 Sheets-Sheet l.

s I l c A A d MS INVENTOR Peter SCHMIDT viz-MI f/n-m his ATTORNEY 3,521,606 FUEL INJECTION CONTROL ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Peter Schmidt, Stuttgart-Botnang, Germany, assignor to Robert Bosch G.m.h.H., Stuttgart, Germany Filed Oct. 18, 1968, Ser. No. 768,793 Claims priority, application Germany, Oct. 21, 1967,

US. Cl. 123-32 10 Claims ABSTRACT OF THE DISCLOSURE its base-emitter path. A voltage divider is connected to the emitter of the emitter-follower transistor. The monostable multivibrator is provided with a transformer which determines the timing of the multivibrator, and which has its secondary winding connected to the voltage divider and to the base of the input transistor of the monostable multivibrator.

BACKGROUND OF THE INVENTION The present invention resides in a control arrangement for the operation of at least one electromagnetic injection valve associated with an injection arrangement of an internal combustion engine. A monostable multivibrator is provided with an input transistor and an output transistor for realizing rectangular-shaped pulses determining the opening duration of the injection valves. The duration of the pulses are variable as a function of the rotational speed, through a control voltage applied to the base of the input transistor. The control voltage has a varying waveform in phase with the switching pulses. The variation of the control voltage is periodically in phase with the switching pulses. The control voltage is realized through a control circuit arrangement which includes at least two switching transistors with time delays in relation to the end of the leading switching pulse. The first one of these two transistors is connected with its base, to the collector of the aforementioned input transistor, by way of a capacitor.

\In injection arrangements of this species, the quantity of fuel supplied to the internal combustion engine for each operating cycle is determined through the prevailing duration in which the associated injection valve is open. The fuel is supplied under substantially constant pressure. For the purpose of varying the duration of the switching pulse, the feedback circuit of the monostable multivibrator includes an electrical energy storage device consisting of a ferromagnetic inductor. The inductance value of this inductor is adjusted through the pressure prevailing in the intake manifold behind the throttle. In order to achieve auxiliary corrections depending upon the rotational speed for application to the pulse duration, it is possible to shorten or lengthen the duration of the unstable state of a multivibrator which has usually constant feedback conditions. This variation in the time duration may be made in accordance with the variation in the control voltage. This control voltage is realized at the end of a switching United States Patent "ice 3,521,606 Patented July 28, 1970 pulse and through a control circuit arrangement which includes two or more operating switching transistors. Such an arrangement is disclosed in the US. Pat. 3,338,221. In a known control arrangement of this species, further, as shown in the German Pat. 1,231,954, a chain of storage capacitors are provided through interconnecting resistors. The voltage set at the end of the chain is coupled, by way of a resistor to the emitter-base circuit of the input transistor associated with the monostable multivibrator. As a result of this type of coupling, it is necessary to use relatively large storage capacitors, since the resistors functioning in conjunction with these capacitors, may only have small values. Aside from this, difficulties arise with respect to varying the individual values of the resistors because considerably complex and only difiicult changes in the waveform of the control voltage and the duration of the opening pulse is realizable. In this arrangement, furthermore, the control arrangement is based on a fixed relationship between the rotational speed and the opening duration of the injection valve of the internal combustion engine.

In order to overcome these difficulties, a control voltage is generated from a control circuit arrangement for applying corrections to the opening pulse duration as a unction of the rotational speed. A switching transistor following this control circuit arrangement operates in conjunction with a diode and a collector resistor connected in parallel to a storage capacitor. A further resistor is parallel with this storage capacitor. This resistor lies in the base-collector circuit of an emitter-follower transistor with emitter connected preferably through a resistor, to the tap or a junction of a voltage divider. A transformer serves as a timing element of the multivibrator, and the secondary winding of this transformer is connected, at one terminal, to the base of the input transistor. The other terminal of the secondary winding of the transformer is connected to the above voltage divider, furthermore.

SUMMARY OF THE INVENTION An arrangement for controlling the injection of fuel in internal combustion engines. The fuel is controlled through an electromagnetically actuated injection valve. The pulses for actuating the valve are derived from a monostable multivibrator circuit, in which the timing is regulated through a variable core transformer connected to the intake manifold of the engine. The monostable multivibrator circuit is provided with an input transistor and an output transistor. A control circuit generates a control voltage which varies the duration of the pulses emitted by the monostable multivibrator, as a function of the speed of the engine. The control circuit includes a first transistor with its base connected to the collector of the input transistor of the monostabe multivibrator. A coupling capacitor is interposed between the base of this first transistor and the collector of the input transistor. The control circuit also includes a second transistor with collector connected to a resistance-capacitance network. An emitter-follower transistor at the output of the control circuit has its base-emitter path connected to the resistance-capacitance network. A voltage divider in the monostable multivibrator circuit has a junction or tap connected to the emitter of the emitter-follower transistor. The secondary winding of the timing transformer within the monostable multivibrator circuit has one terminal connected to the aforementioned tap or junction of the voltage divider, and the other terminal connected to the base of the input transistor.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electrical schematic diagram and shows the electrical circuitry for controlling the injection apparatus of an internal combustion engine denoted in functional form;

FIG. 2 is a graphical representation of the function of the opening duration of the injection valves as a function of engine speed, to be achieved through the circuit arrangement in FIG. 1;

FIG. 3 is a waveform representation of electrical signals associated with the circuitry of FIG. l;

FIG. 4 is a second embodiment of the control circuit shown in FIG. 1;

FIG. 5 is a graphical representation of the opening duration of the injection valves as a function of engine speed, corresponding to the circuit of FIG. 4;

FIG. 6 shows three waveform diagrams of voltage signals associated with the circuit of FIG. 4;

FIG. 7 is an electrical schematic diagram and shows a third embodiment of the control circuit of FIG. 1;

FIG. 8 is a graphical representation of the function of injection time versus engine speed, to be realized by the circuit of FIG. 7;

FIG. 9 shows five waveform diagrams of signals associated with the circuit of FIG. 7;

FIG. 10 is a further embodiment of the control illustrated in FIGS. 4 and 7;

FIG. 11 is a graphical representation of the functional characteristics associated with the circuit of FIG. 10, and illustrates the function of the injection time interval in relation to engine speed; and

FIG. 12 shows a series of waveform diagrams of electrical signals as a function of time, associated with the circuit of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, the fuel injection arrangement shown in FIG. 1 is designed for operating a four cylinder internal combustion engine. The spark plugs 2 of the engine are connected to a high voltage ignition arrangement, not shown. In direct proximity of the intake valves, not shown, of the internal combustion engine, an

circuit electromagnetically actuated injection valve 4 is situated for each individual cylinder. This injection valve 4 is located on the branches of the intake manifold 3 leading to the individual cylinders. Fuel from a distributor 6 is led to each valve, by way of the individual fuel lines 5. The fuel within the distributor and in the lines 5, is maintained substantially constant at a pressure of approximately 2 atmospheres, by means of an electrical motor and pump combination 7.

Each of the injection valves 4 has a magnetizing coil, not shown, with one end of the coil connected to ground and the other end connected to a respective resistor 9 by way of the associated connecting circuit at 8. The resistors 9 are separated in pairs and each pair has joined together when at a common point two ends of the resistors, and this common point is in turn connected to the collector of one of the transistors 10, 11. These transistors function as power transistors in an electronic regulating and control arrangement to be described.

Aside from these power transistors 10 and 11, the regulating and control arrangement includes a monostable multivibrator circuit .12 dilineated in the drawing by dashed lines. This monostable multivibrator circuit is designed to produce electrical pulses, and has an input transistor T an output transistor T as well as a timing element in the form of a choke or inductance 13.

The choke or inductance 13 is designed in the form of a transformer having an adjustable core. The core is coupled to the membrance of a pressure device 16, by way of a positioning bar or rod 15. The pressure device communicates with the intake manifold 3 through its suc tion side, and is located directly after the adjustable throttle 18 positioned by means of the foot pedal 17. When the pressure within the intake manifold of the engine drops. the membrane within the pressure device 16 lifts the core '14 in the direction of the arrow indicated in the drawing, and thereby produces larger air gap within the core of the transformer. As a result of this increased air gap, the inductance of the primary winding 19 of the transformer, becomes decreased to the extent that this inductance of within the intake manifold 3.

The secondary winding 20 of the inductor 13 has one end connected to the base of the transistor T and leads to the positive voltage terminal 21, by way of the resistor R The other end of the secondary winding 20 is connected to a junction H. A resistor R is connected between the junction H and the positive terminal 21 of the voltage supply. This junction H also leads to the negative terminal 30 of the voltage supply, via the resistor R The resistors R and R form a voltage divider and are connected across the voltage terminals. The junction H is a tap of this voltage divider. The negative designated voltage terminal 30 is connected to ground and to the negative terminal of a 12-volt battery, not shown. The two transistors T and T are both of the npn type and have their emitters directly connected to the negative terminal 30. The collector of the transistor T leads to the positive terminal 21, by way of the R The collector of the transistor T on the other hand, is connected to the positive terminal 21 throught he series circuit path of the primary winding \19 and the resistor R The base of the transistor T is connected to the collector of the transistor T through a coupling resistor R The base of the transistor T is connected in series with a differentiating capacitor C which, in turn, connected to the fixed contact 23 of a switch having a switching arm 24 connected to the negative terminal or circuit path 30. The switching arm 24 is actauted by a cam 28 having two lobes. The cam is mechanically coupled to the crank shaft 27 of the engine and is rotatably driven by this crank shaft. As a result, the cam closes the switching arm 24 for every rotation of the crank shaft, and thereby turns off the transistor T For the purpose of charging and discharging the capacitor C one electrode of this capacitor is connected to the fixed contact 23 and to the positive terminal circuit path 21, by way of the resistor 29. The other electrode of the capacitor C leads to the positive terminal 21 by way of the resistor R At the same time, this other electrode of the capacitor C is also connected to the secondary winding 20 which leads to the junction H.

Before describing the other elements of the control arrangement, an illustration will be provided as to how the opening duration of the injection valves 4 is determined by the current pulses whenever the swtiching contacts 23 and 24 become closed. This illustration is based on variation of the pressure within the intake mani fold 3 and the accompanying variation in the inductance of the primary winding 19.

Directly prior to the individual closing instants of the switching arm 24, the input transistor T is turned on and thereby maintains the output transistor T in the turned off state. As soon as the switching arm 24 comes into contact with the fixed switching contact 23 as a result of the action of the cam 28, the stored charge in the capacitor C drops the base potential of the input transistor T below the potential of the negative terminal 30. This dropping of the base potential is in the negative region. As a result, the transistor T is turned off and the multivibrator circuit 12 becomes transferred to its unstable operating state, in which a transistor T is turned on. The transistor T then tends toward an exponentially increasing collector current which flows through the primary winding 19. This increasing current through the primray winding 19 gives rise, in turn, to a correspondingly increasing magnetic field through the ferromagnetic core 14 which is adjustable in the transformer. The increase or rise in the current is more rap d, the larger the ai gap and the smaller the deceasing 1nductance of the primary winding 19. This inductance decreases with increase in air gap. With this rise in current, a feedback voltage is induced in the secondary Winding 20. This feedback voltage decreases exponentially from its maximum value determined at the instant of closure of the switching contacts 23 and 24. The speed of variation of this feedback voltage is determined by the magnitude of the inductance. The feedback voltage is of such polarity that it tends to maintain the input transistor T turned otf. The feedback voltage, thereby acts against the positive base potential, through resistor R which seeks to return the input transistor T to its stable state in which it is turned on. This occurs when the induced feedback voltage in the secondary winding is smaller than the base potential.

As long as the transistor T is turned off, the turned on transistor T maintins the power transistors 10 or 11 also in the turned on or conducting state, by way of the amplifier 32. However, as soon as the transistor T is returned to its stable or turned on operating state, the transistor T T and T become again turned off. The duration of the pulse I which determines the opening of the injection valves 4, is therefore established from the instant of closure of the switch 24, to the instant at which the output transistor T becomes turned off and the input transistor T becomes again turned on and in the conducting state. When the inductance of the primary winding 19 decreases as a result of decreased pressure in the intake manifold 3, the collector current of the transistor T can rise more rapidly. The feedback voltage induced within the secondary winding 20, thereby, decreases also more rapidly, and the input transistor T returns to its turned on state in which was earlier. In this case, injection valves 4 become essentially closed at an earlier instant than in the previous case accompanied by greater inductance and greater pressure within the intake manifold 3.

Through the variation of the inductance of the primary winding 19, as described, the duration of the opening pulse I of the injection valves, becomes a function of the prevailing pressure of the internal combustion engine. Experimental results realized from vehicle operation and laboratory conditions have, however, shown that the quantity of fuel to be injected must be made a function also of the rotational speed of the engine, in addition to the prevailing vacuum within the manifold. The pulse durations established for a prevailing pressure have the same magnitude for a given pressure, independent of the rotational speed. As a result, an additional control circuit A is provided in conjunction with regulating and control arrangement of FIG. 1. The additional control circuit A varies periodically with the injection processes, the voltage appearing between the junction H and the negative terminal or circuit path 30. The control circuit provides, for this purpose, a control voltage U having a wave form shown in FIG. 3d.

The pulse duration T of the next pulse J is determined from the instantaneous value of the control voltage U associated with the next end of the pulse. Accordingly, a period of time t prevails between the instant of time that the control voltage is established and the instant of time at which thiscontrol voltage determines the pulse duration with its instantaneous value. As a result a fixed arrangement is realized between the pulse durations t and the period of time t corresponding to the rotation al speed of a internal combustion engine.

The control circuit arrangement A in FIG. 1 serves to provide for a feature that the duration t, of the opening pulse be made a function of the rotational speed, as shown in FIG. 2. In accordance with this graphical representation of FIG. 2, the opening pulses should have a constant duration with increase in engine speed It until a speed n =10O0 revolutions per minute is attained. Between the speeds n and n =4000 revolutions per minute, the duration of the opening pulses first rapidly increase and then level off as the speed approaches the magnitude n For operating speeds beyond 11 the time durations are essentially constant.

The control circuit A includes a first switching transistor T with base connected to a timing network consisting of capacitor C connected in series with a resistor R The resistor is in turn, connected to the junction G leading to the positive terminal 21, by way of the resistor R The timing network consisting of the capactor C and resistor R provides a constant delay time t The junction G is also the collector of the input transistor T The emitter of the first switching transistor T is connected to the negative terminal of the voltage supply, similar to that for transistors T and T The base of the transistor T leads to the positive terminal 21 of the voltage supply, by way of the base resistor R The base of the second transistor T leads also to the positive terminal 21, through the resistor R At the same time, this base of the switching transistor T is also connected to the collector of the first switching transistor T by way of the timing capacitor C The coupling capacitor C also provides a constant delay time t The transistors T and T are maintained in their turned on state or conducting state when in their non-operating or quiescent state. Through the resistor R connected between the collector of the transistor T4, and the base of transistor T the latter is maintained in the turned off or non-conducting state, when in the non-operation or quiescent state. The collector of the transistor T is connected to a voltage divider consisting of resistors R and R The junction of these two resistors of the voltage divider is, in turn, connected to a diode D leading to a capacitor C; with one electrode connected to the positive terminal or circuit path 21. When in the turned on state, the transistor T causes rapid charging of the storage capacitor C through the diode D A discharge resistor R is connected in parallel with the capacitor C A resulting voltage on the storage capacitor C, When charging and discharging, is used for the purpose of forming the control voltage. The formation of this voltage, is however, not achieved directly, but instead through an intermediate emitter follower transistor T The collector of this transistor T is directly connected to the positive terminal or circuit path 21, and the base of the transistor is connected to the storage capacitor C As a result of the transistor T it is possible to achieve long discharge times with a relatively small capacitor C and a large resistor R Thus, the interacting effects between the resistor R and the voltage divider characteristics of the resistors R and R are avoided, when one of these resistors becomes varied for adjusting or setting to a desired speed eifect.

In the operation of the control circuit arrangement A, a negative step voltage appears at the collector of the transistor T of the multivibrator 12, at the end of the time interval t This step voltage turns off the transistor T by way of the resistor R and capacitor C The negative step voltage apperaing at the base of the transistor T is applied towards the resistor R after going through an e or exponential transfer function. After the time interval i determined by the magnitude of the capacitor C the transistor T becomes again conducting. A negative step voltage appears, thereby, at the collector of the switching transistor T and this step voltage reaches the base of the transistor T by way of the capacitor C The transistor T is turned on in the non-operating or quiescent state.

With the negative step voltage reaching the base of the transistor T the latter becomes turned off, and remains in this turned olf state, until the potential of its base changes through the resistor R so that a base potential becomes positive in relation to the emitter of the transistor T The function of the collector potentials of the transistors T T and T are shown in FIG. 3a-c. The pulses appearing at the collector of the transistor T become cancelled through the transistor T Thus, as long as the transistor T is turned on, the transistor T is turned off, and vice-versa. When the transistor T is turned on or conducts, the capacitor C becomes charged, through the diode D and the resistor R The charge upon the capacitor C is such that the resulting potential drop across the capacitor is determined by the voltage divider R R When the transistor T becomes turned off, the capacitor C discharges with a large time constant through the resistor R and the high input resistance of the transistor T The capacitor 0., cannot discharge completely. Through the diode D a remaining potential is maintained on the capacitor C which is determined by the voltage divider R R A control voltage U appears at the output of the control circuit arrangement A. This control voltage becomes amplified by the transistor T and reaches the junction H by way of the resistor R This junction point H is the junction of the voltage divider R -R This control voltage U determines the pulse duration of the control multivibrator circuit. FIG. 3a shows the function of the control voltage U appearing between the emitter of transistor T and the positive terminal or circuit path 21. The control voltage U begins with large negative values at the end of a delay time interval 1., determined by the second timingnetwork consisting of the capacitor C resistor R and transistor T in accordance with FIG. 1. From its initial value, the control voltage U follows an exponential function of 0 function. When the control voltage becomes positive in relation to the potential U determined by the voltage divider R1e-R17, the diode D is driven to the conducting state. In its initial state, the diode D is non-conducting. The diode D maintains the control voltage at the resulting value, in the form of a threshold level. At the end of the delay time interval 1 the capacitor 0., becomes charged with a small time constant, in accordance with FIG. 3b or FIG. 30 for the beginning of the pulse of the second timing network. The control voltage U attains rapidly large negative values which are maintained until the end of the second delay time interval t.;.

In realizing the injection duration 1, as a function of the rotational speed 11, in accordance with FIG. 2, the pulse duration t, is determined directly by the instantaneous value of the control voltage U before the end of the pulse. When the rotational speed is lower than n the control voltage is at the level U as shown in FIG. 3. Thus, the pulse duration t, is constant. The duration z is inversely proportional to the rotational speed, and as a result t becomes smaller with increasing rotational speed 11. Between the rotational speeds I1 and n the end of the pulse duration t falls within that region, in which it is larger depending upon the control voltage U As a result, t becomes larger with increasing rotational speed n. At the rotational speed n the duration t is so large as the sum of the delay time interval t and the delay interval t These two time intervals correspond to the first timing network of FIG. 3b and the second timing network of FIG. 3c, respectively. Thus, the end of the pulse duration t occurs simultaneously with the end of the delay time interval L; of the second timing network. For rotational speeds exceeding n the second delay time interval cannot be fully realized, since the first timing network of capacitor C transistor T and resistor R becomes newly actuated at the end of the pulse duration t Thus, the transistor T becomes turned off and, at the same time, the transistor T becomes again conducting or turned on through the positive step voltage transmitted through the capacitor C The control voltage U is thereby always at large negative values, and the pulse duration is constant for rotational speeds exceeding 11 As a result, the function of the pulse duration 1, is realized in relation to the rotational speed, as shown in FIG. 2. The rotational speeds n, may be varied through variation in the threshold voltage level U which, in turn, may be varied through the voltage divider R16R17. The rotational speeds 11 may be varied through shifting of the combined times of the timing networks determined by the switching transistors T and T; as well as their coupling capacitors C and C The control circuit arrangement shown in FIG. 4, serves to produce the function of the pulse duration 1, in relation to the rotational speeds n, as shown in FIG. 5. This becomes achieved through the superposition of two control voltages, in which one serves for the rise in the pulse time interval t and the other for the drop in this time interval.

The control circuit arrangement B has similarly a separate stage E containing an emitter follower transistor T which leads to the circuit junction H of the multivibrator circuit 12. The latter is shown in FIG. 1. The control circuit B includes a first transistor T and a second switching transistor T A coupling resistor R is connected between the collector of the transistor T an dthe base of the transistor T The first switching transistor T; has its base connected to the voltage divider junction G, by way of a resistor R and a capacitor C which determine a constant delay time interval. A base resistor R maintains the transistor T in the conducting or turned on state when in the non-operating or quiescent condition. The resistor R is connected between the base of the transistor T and the voltage terminal or circuit path 21. The transistor T operates in conjunction with a diode D having its anode connected to the collector of the transistor. The transistor also operates in conjunction with a storage capacitor C and a resistor R connected in parallel with this capacitor. These two elements lie together with the diode D parallel to the emitter-collector path of the transistor. The second switching transistor T also operates with a storage capacitor C which is connected in parallel to a discharge resistor R These two components form a parallel circuit with the collector resistor R through the series circuit of the diode D and the resistor R The resistor R is the collector resistor of the transistor T The emitter of the transistor T is, similar to that of transistor T connected directly to the negative circuit path 30. Each of the two capacitors C and C is associated with a diode D and D respectively, leading to the base of the emitter-follower transistor T At the same time, these two diodes D and D are also connected to the resistor R leading to the negative voltage circuit path 30.

In the detailed functional operation of the switching circuit, the back end of the opening pulse of FIG. 6a actuates a timing network at the end of the duration t The timing interval of this timing network is determined by the capacitor C and the resistor R During this time, the transistor T is turned off (see FIG. 6b) and the capacitor C becomes charged to a positive potential through the diode D and the resistor R The charging time of this capacitor is with a substantially small time constant. The transistor T1 is turned on in its quiescent or non-operating state. After the expiration of the delay time interval t the diode D becomes non-conducting and the capacitor C discharges across the high ohmic resistor R With large time constant. In this circuit state, the transistor T is again turned on. The discharge current through the diode D and the resistor R which is of high ohmic value, can be substantially neglected. As a result, the voltage function I as shown in FIG. 6c is realized across the capacitor C The transistor T is a part of an inverting stage which cancels the signal appearing at the collector of the transistor T During the time interval t-; of the timing network, the transistor T is turned off and the transistor T is turned on or in the conducting state. Accordingly, the capacitor G; can become charged to a negative potential, with small time constant, by way of the diode D and the resistor R When the transistor T becomes again turned off, the diode D also becomes non-conducting, and the capacitor C discharges with large time constant through the resistor R As a result, the function II shown in FIG. 60 is realized across the capacitor C At the output of the control circuit arrangement B, the voltage signal U is composed of the two curves I and II. The composition is such that the curve of FIG. 6c is realized, in which case either the diode D or the diode D conducts depending upon a smaller prevailing voltage. The voltage U becomes still amplified by the transistor T and then reaches the voltage divider R R by way of the resistor R The voltage U thereby infiuences or affects the pulse durations t The pulse diagrams of FIG. 6 are shown for a rotational speed exceeding 11;. In this relationship the back edge of the pulse duration 1!, falls in accordance with the rise in the control voltage. For rotational speeds below n,, the control voltage is zero, and the resulting pulse duration t, is constant. It is also possible to provide a threshold level similar to the circuit of FIG. 1. At the rotational speeds n the pulse duration attains its maximum value and then drops again, since the control voltage becomes smaller. The timing network in FIG. 6b is so adjusted, in accordance with the present invention, that the time interval t7 is smaller than the duration 1 corresponding to the highest rotational speed.

The control circuit arrangement of FIG. 7 serves the purpose of applying the speed correction of the opening pulse duration t,, as shown in FIG. 8. In this curve or function, the pulse duration t, has its maximum value up to the rotational speed n and then drops to the rotational speed 11 at a decline. .The curve then increases again similar to the curve shown in FIG. 2, until the rotational speed 11 is attained. After that speed, the curve remains substantially constant.

The control voltage arrangement in FIG. 7, is composed of two portions A and C. These two portions produce two voltages U and'U These two voltages then become superimposed, and the control voltage U is realized. The circuit portion A differs from the circuit portion A of FIG. 1, solely in the aspect that here no limiting element or network is provided. The resulting voltage U appearing at its output, is again shown in FIG. 9b. This voltage serves to determine the pulse duration t, for rotational speeds exceeding 11 With the back edge of the pulse of the second timing network in circuit portion A, a third timing network becomes actuated. This third timing network consists of capacitor C the resistor R and the transistor T This actuation of the third timing network is realized when the transistor T is again in the conducting state or is turned on. During this period of time, the transistor T which is turned on in the quiescent state, becomes turned off. The capacitor C thereby charges, with substantially small time constant, to a positive potential through resistor R and diode D When the transistor T is again turned on (see also FIG. 90), the diode D becomes non-conducting and the capacitor C discharges, with substantially large time constant through the resistor R The resulting voltage U; appearing at the output of the circuit portion C is shown in FIG. 9d. The two voltages U and U are combined to form the control voltage U Depending upon which voltage is larger, it reaches the base of the transistor T through the diodes D and D As a result, the amplified control voltage U at the emitter of the transistor T is realized as shown in FIG. 9e. The pulse diagrams in FIG. 9 represent those conditions which correspond to a rotational speed between 11 and n If the rotational speed becomes smaller or the time period becomes larger, the control voltage becomes larger at the end of the pulse duration t, and the latter increases with decreasing rotational speed until the speed 11 is attained. For speeds less than 11 the pulse duration t, then remains constant, since a control voltage has attained its maximum value. The control voltage attains its minimum value at the rotational speeds 11 and then increases again with increasing rotational speed. This minimum value may be shifted over a wide range through variation in the time interval associated with the third timing network of FIG. 90. With larger rotational speeds, the capacitor C cannot discharge completely. Thus, the voltage U becomes smaller, and the control voltage is identical with the function of the voltage U As a result, the function of the pulse duration t shown in FIG. 2, is realized.

FIG. 11 shows a curve which is practically the same as the curve shown in FIG. 8, until the rotational speed 11 is attained. For rotational speeds larger than n the pulse duration 2 decreases again. FIG. 10 shows the control circuit by which this curve becomes realized. This circuit is composed essentially of the circuit portions B and C, which have already been described. The voltage U appearing at the output of circuit portion B is again reproduced in FIG. 12b in the form of an extended curve. This voltage becomes amplified through the transistor T and reaches the base of the transistor T by way of diode D In relating the circuit portion C with the circuit portion B, the timing network in the circuit portion C becomes actuated through the capacitor C after the expiration of the delay time interval of the circuit portion B. This corresponds to the condition when the transistor T becomes again conducting or in the turned on state. The voltage U appearing at the output of the circuit portion C is shown in FIG. 12c. The transistor T becomes controlled by the diodes D and D depending upon which one is associated with the larger voltage. The diodes are biassed for this purpose. As a result, the control voltage U is realized at the emitter, as shown in FIG. 120, which shows an extended curve. The pulse dura tion t, as a function of the control voltage U or of the rotational speed is again realized as described supra. It is only necessary to be certain that the time interval t associated with the timing network of the capacitor C transistor T and resistor R of the circuit portion B, is smaller than the period i corresponding to the maximum rotational speed.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in controlled injection arrangements for internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A control arrangement for controlling the injection means of an internal combustion engine comprising, in combination, at least one electromagnetically operated injection valve in said injection means; monostable multivi'brator means with input transistor and output transistor for generating rectangular-shaped pulses determining the duration of the opening of said injection valve; control circuit means generating a control voltage for varying the duration of said pulses as a function of the speed of said engine; a first transistor in said control circuit means with base connected to the collector of said input transistor; coupling capacitor means connected between the base of said first transistor and said collector of said input transistor; a second transistor in said control circuit means and connected to said first transistor; a resisttance-capacitance network connected to the collector of said second transistor; an emitter-follower transistor with base-emitter path connected to said resistance-capacitance network; voltage dividing means connected to the emitter of said emitter-follower transistor; and transformer means in said monostable multivibrator means for determining the timing of the same, one terminalof the secondary winding of said transformer means being connected to said voltage dividing means and the other terminal of said secondary winding being connected to the base of said input transistor.

2. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 1 wherein said resistance-capacitance network comprises a collector resistor in series with the collector circuit of said second transistor; a diode having one terminal connected to the collector of said second transistor; and storage capacitor means with one electrode connected to the other terminal of said diode and the other electrode connected to said collector resistor.

3. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 2 including auxiliary resistor means connected in parallel with said storage capacitor means.

4. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 3 including coupling resistor means connected between the emitter of said emitter-follower transistor and said voltage dividing means.

5. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 4 including additional voltage dividing means in said control circuit means; and additional diode means connected between said additional voltage dividing means and said storage capacitor means.

6. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 4 including further storage capacitor means connected in parallel with the emitter-collector path of said first transistor; a third diode connected between the collector of said first transistor and said further storage capacitor; a third resistor connected in parallel with said further stroage capacitor; a fourth diode connected between the junction of said third resistor and said further storage capacitor and the base of said emitter-follower transistor; and a fifth diode connected in series with the base of the emitter-follower transistor.

7. A control arrangement for controlling the injection means of an internal combustion engine as defined in claim 6 including auxiliary switching circuit means connected in series with the base of said emitter-follower transistor and having an auxiliary transistor with base connected to the collector of said first transistor; second coupling capacitor means connected in series with the base of said auxiliary transistor; a series combination of a sixth diode and a sixth storage capacitor connected in parallel with the emitter-collector path of said auxiliary transistor; and a sixth resistor connected in parallel with said sixth storage capacitor.

8. A control arrangement for controlling the injection means f0 an internal combustion engine as defined in claim 7 including a coupling diode in series with the base of said emitter-follower transistor for decoupling said storage capacitors from said emitter-follower transistor.

9. A control arrangement for contolling the injetcion means of an internal combustion engine as defined in claim 1 including mechanical linkage means linking the core of said transformer means with the intake manifold of said engine for varying the inductance of said transformer means as a function of the presure prevailing within said intake manifold.

10. A control arrangement for controlling the injection means of aninternal combustion engine as defined in claim 1 including amplifier means connected between said monostable multivibrator means and said electromagnetically operated injection valve.

References Cited UNITED STATES PATENTS 3,338,221 8/1967 Scholl.

LAURENCE M. GOODRIDGE, Primary Examiner UJS. c1. X.R. 

